Environmentally Friendly Trivalent Chromium To Hard Chrome Plating

It is urgent to develop the technique of trivalent hard chromium plating because of the heavy pollution of hexavalent hard chromium plating. It is significant and meaningful to study the technique of trivalent hard chromium plating, thereby popularizing the application for the reality, breaking the barriers of overseas technology and achieving our cleaner productions of electroplating industry. Therefore, study on the trivalent hard chromium electroplating proeess, and make it apply on mass production have highly realistic and strategieal significance to breaking through the overseas technical barrier and achieving the goal of Clean Production in Chinese electroplating industry.Electroplating with trivalent chromium in sulfate system was deeply studied by means of Hull cell testing, small size cell rack-plating testing and enlargement experiment and so on. Suitable technical conditions of trivalent chromium electroplating were determined by the means of Hull cell testing, through the single factor experiment, the influence on trivalent chromium electroplating by technical conditions was studied intensively, such as concentration of major salt, cathodic current density, temperature, pH, plating time and so on. Through orthogonal experiment, technical conditions of trivalent chromium electroplating were optimized deeply. Finally, the stability of the trivalent chromium plating bath was studied based on the results of the single factor and the orthogonal experiments, which were confirmed by enlargement experiment.A series of research approachs were used to research various performance of trivalent chromium plating bath, and comparison with the hexavalent chromium plating bath. Experimental results showed that trivalent chromium plating bath has good stability, even-plating capacity and deepening plating ability, cathode polarizing capability, cathode current efficiency were better than the hexavalent chromium plating bath.Scanning electron microscope(SEM), X-ray diffraction (XRD) and other modern test methods were used to preliminary study various performance of trivalent chromium coatings, experimental results showed that trivalent chromium plating could reach the performance of the production demands, even exceed the performance of hexavalent chromium plating, but the thickness of trivalent chromium plating was less than hexavalent chromium plating's.Titanium based DSA anode performance were tested by measuring steady-state polarization curves and small size cell rack-plating testing. Experimental results showed that the DSA anode had long service life, good abilities of evolution of oxygen and also could restrain trivalent chromium becoming to hexavalent chromium. Therefore, the DSA anode was the most suitable for trivalent chromium plating anode.